Electromagnetic & transducer sound sources: radios, coils & tape heads

Every room you perform in is already full of sound you cannot hear: motors, laptops, fluorescent ballasts, and card stripes all radiate electromagnetic activity. This module builds toward a whole task in the Collins hardware-hacking lineage — assembling a rig that turns that invisible weather into a performable instrument, then recording an exploratory piece with it. In an experimental or noise set, this rig is a legitimate sound source alongside your synths: cheap, tactile, and impossible to fake with plugins.

The arc starts supported. First, understand why a coil of wire near a magnetic field is already a microphone, then tune a thrift-store AM radio to a dead band and sweep it around your studio — the eavesdropping and circuit-sniffing procedures are your just-in-time how-to for mapping a laptop or mixer’s electromagnetic signature. From there you go hands-on-circuit: the radio body-synthesizer technique (damp fingers on an exposed, battery-powered board) turns listening into playing. In parallel, salvage a tape head and wire it as a hand-played scratcher over tape and card stripes. Cabling everything without hum forces the shielded-cable and signal/ground principle into practice, and speaker/mic reversibility explains why your transducers work in both directions — both are things you must articulate, not just do.

The required atoms gate the capstone directly: you cannot assemble, wire, or perform the rig — or explain it — without them. The supporting atoms widen the territory: the electret build offers an alternative capsule for the rig’s second voice, the shielded-cable fact reinforces the grounding rule, and video-to-audio transduction, Bela, and biodata sketch where transducer thinking leads next — from salvaged heads to embedded, sensor-driven instruments.